HONOLULU — A team trying to solve the mystery of Amelia Earhart's fate 75 years after she vanished over the Pacific has ended its expedition to a remote island without finding her plane, the group said.

Researchers on July 3 set off on a $2.2 million expedition and traveled 1,800 miles by ship from Honolulu to Nikumaroro in the Republic of Kiribati to search for clues to her disappearance in 1937.

Earhart, along with her navigator Fred Noonan, set out to circumnavigate the globe along an equatorial route.

Richard Gillespie, executive director of TIGHAR, has said that he believes Earhart died a castaway in searing hot Nikumaroro, which is 400 miles southeast of the Howland Island destination that Earhart and Noonan had been aiming for when they disappeared. Before radio contact was lost, Earhart had said from the air that her plane was short on fuel.

Gillespie has said evidence found on Nikumaroro in previous expeditions included what appeared to be a bottle of 1930s anti-freckle cream, bits of clothing and human bone fragments, which have led some to believe Earhart and her navigator Fred Noonan may have been marooned on the island.

TIGHAR said on its website that researchers are on their way back to Honolulu after cutting short the expedition due to equipment malfunctions. They spent five days on site, but had planned to be there for 10 days.

Researchers had said they believed Earhart's Lockheed Electra plane could rest in waters off Nikumaroro, where they suspect she survived for weeks or months.

During the five days they spent searching, the crew of expedition ship Niku VII was challenged by the undersea environment, in the form of a craggy reef slope with vertical cliffs stretching down for between 110 feet and 250 feet, the group said on its website.

On July 19, the expedition's blog questioned whether an aircraft that sank 75 years ago could even be found. Not only is the area filled with nooks, crannies and caves, but it is possible the aircraft might have floated away, the group said.

Pat Thrasher, president of TIGHAR, said the Niku VII expedition crew will arrive in Honolulu at the end of this month, at which point Gillespie, who was on the expedition, will be available to answer questions.

Once the crew returns to land, the TIGHAR team will review and analyze the new material. The search for answers to Earhart's disappearance was documented for a Discovery Channel television special set to air on August 19.